Alkaline negative electrolyte and alkaline zinc-iron flow battery assembled by same

Abstract

An alkaline negative electrolyte and alkaline zinc-iron flow battery assembled by same are provided. The alkaline negative electrolyte includes zinc ions, a complexing agent, and alkali; the complexing agent is at least one selected from the group consisting of ethylenediaminetetraacetic acid, ethylene glycol diethyl ether diamine tetraacetic acid, cyclohexane tetraacetic acid, and ethylenediamine tetrapropionic acid; a molar ratio of the zinc ions to the complexing agent is 1:1; and a molar ratio of the complexing agent to the alkali is 1:(3-4). The zinc ions in the negative electrolyte are in form of a complex state, which is used as the negative electrolyte to assemble and obtain the alkaline zinc-iron flow battery, solves the problem of electrolyte migration in alkaline zinc-iron flow battery and improves the cycling stability of the battery; moreover, it improves the low-temperature performance of the battery, and broadens the operating temperature range of alkaline zinc-iron flow battery.

What is claimed is: 
     
         1 . An alkaline negative electrolyte, wherein the alkaline negative electrolyte comprises zinc ions, a complexing agent, and alkali;
 the complexing agent is at least one selected from the group consisting of ethylenediaminetetraacetic acid, ethylene glycol diethyl ether diamine tetraacetic acid, cyclohexane tetraacetic acid, and ethylenediamine tetrapropionic acid;   a molar ratio of the zinc ions to the complexing agent is 1:1; and   a molar ratio of the complexing agent to the alkali is 1:(3-4).   
     
     
         2 . The alkaline negative electrolyte according to  claim 1 , wherein a concentration of the zinc ions is from 0.1 mol·L −1  to 2 mol·L −1 . 
     
     
         3 . The alkaline negative electrolyte according to  claim 1 , wherein a concentration of the zinc ions is from 0.2 mol·L −1  to 1 mol·L −1 . 
     
     
         4 . A method of preparing the alkaline negative electrolyte according to  claim 1 , comprising the following steps:
 dissolving the alkali, and adding the complexing agent, followed by a zinc salt; when completely dissolved, adjusting a pH to 9-13.   
     
     
         5 . The alkaline negative electrolyte according to  claim 1 , wherein the zinc salt is at least one selected from the group consisting of zinc sulfate, zinc bromide, zinc chloride, zinc nitrate, zinc acetate, zinc trifluoromethanesulfonate, zinc bis(trifluoromethylsulfonyl)imide, zinc tetrafluoroborate, zinc hexafluorophosphate, and zinc bis(oxalate) borate. 
     
     
         6 . The alkaline negative electrolyte according to  claim 1 , wherein the alkali is at least one of NaOH and KOH. 
     
     
         7 . An alkaline zinc-iron flow battery, comprising a positive electrode, a positive electrolyte, a separator, a negative electrode, and a negative electrolyte; wherein
 the negative electrolyte is the alkaline negative electrolyte according to  claim 1 .   
     
     
         8 . The alkaline zinc-iron flow battery according to  claim 7 , wherein the positive electrolyte comprises Fe(CN) 6   4−  and the alkali;
 the alkali is at least one of NaOH and KOH. 
 
     
     
         9 . The alkaline zinc-iron flow battery according to  claim 8 , wherein a concentration of the Fe(CN) 6   4−  in the positive electrolyte is from 0.4 M to 2 M;
 a concentration of OH in the positive electrolyte is from 0.4 M to 2 M. 
 
     
     
         10 . The alkaline zinc-iron flow battery according to  claim 8 , wherein a concentration of the Fe(CN) 6   4−  in the positive electrolyte is from 0.6 M to 1 M;
 a concentration of OH in the positive electrolyte is from 0.6 M to 1 M. 
 
     
     
         11 . The alkaline zinc-iron flow battery according to  claim 7 , wherein the separator is selected from one of an ion-conducting membrane and a Nafion membrane;
 an electrode material of the positive electrode and the negative electrode is selected from one of graphite felt and carbon felt.   
     
     
         12 . The alkaline zinc-iron flow battery according to  claim 7 , wherein the separator is selected from a polybenzimidazole ion-conducting membrane or a sulfonated polyether ether ketone ion-conducting membrane. 
     
     
         13 . A method of preparing the alkaline negative electrolyte according to  claim 2 , comprising the following steps:
 dissolving the alkali, and adding the complexing agent, followed by a zinc salt; when completely dissolved, adjusting a pH to 9-13.   
     
     
         14 . A method of preparing the alkaline negative electrolyte according to  claim 3 , comprising the following steps:
 dissolving the alkali, and adding the complexing agent, followed by a zinc salt; when completely dissolved, adjusting a pH to 9-13.   
     
     
         15 . An alkaline zinc-iron flow battery, comprising a positive electrode, a positive electrolyte, a separator, a negative electrode, and a negative electrolyte; wherein
 the negative electrolyte is the alkaline negative electrolyte according to  claim 2 .   
     
     
         16 . An alkaline zinc-iron flow battery, comprising a positive electrode, a positive electrolyte, a separator, a negative electrode, and a negative electrolyte; wherein
 the negative electrolyte is the alkaline negative electrolyte according to  claim 3 .   
     
     
         17 . The alkaline zinc-iron flow battery according to  claim 15 , wherein the positive electrolyte comprises Fe(CN) 6   4−  and the alkali;
 the alkali is at least one of NaOH and KOH. 
 
     
     
         18 . The alkaline zinc-iron flow battery according to  claim 16 , wherein the positive electrolyte comprises Fe(CN) 6   4−  and the alkali;
 the alkali is at least one of NaOH and KOH. 
 
     
     
         19 . The alkaline zinc-iron flow battery according to  claim 17 , wherein a concentration of the Fe(CN) 6   4−  in the positive electrolyte is from 0.4 M to 2 M;
 a concentration of OH −  in the positive electrolyte is from 0.4 M to 2 M. 
 
     
     
         20 . The alkaline zinc-iron flow battery according to  claim 18 , wherein a concentration of the Fe(CN) 6   4−  in the positive electrolyte is from 0.4 M to 2 M;
 a concentration of OH in the positive electrolyte is from 0.4 M to 2 M.